Free Metals and Alloys MCQs with Answers

• A. Carbon
• B. Chromium
• C. Titanium
• D. Nickel

Explanation: Titanium stabilizes stainless steel by combining with carbon as titanium carbide, preventing chromium carbide precipitation and preserving…

• A. 100 Mpa
• B. 240 Mpa
• C. 560 Mpa
• D. 700 Mpa

Explanation: Austenitic NiTi has a relatively high yield strength, commonly cited at about 560 MPa in dental-materials data.

• A. Tarnish and corrosion
• B. Thermal conductivity
• C. Warpage
• D. Dimensional change

Explanation: Polishing removes surface irregularities where plaque, moisture, and chemical deposits can accumulate, reducing sites for tarnish and…

• A. Impurities in gold
• B. None of the above
• C. A and B
• D. Improper venting

Explanation: Molten-gold turbulence is primarily related to casting flow, such as excessive pressure or poor sprue design, rather than simply…

• A. High gold
• B. Low gold
• C. Ni - Cr
• D. Palladium - Ag

Explanation: Costume-jewelry allergy most commonly indicates nickel hypersensitivity, so nickel-containing Ni-Cr alloys should be avoided.

• A. Improve bonding
• B. Harden the metal ceramic Ag-Pd alloy
• C. None of the above
• D. Both A and B

Explanation: Indium can harden silver-palladium alloys and forms an oxide that improves chemical bonding between the alloy and porcelain.

• A. 60% cobalt and 30% chrominum
• B. 30% cobalt and 60% chrominum
• C. 1% palladium
• D. 20% gold

Explanation: Typical cobalt-chromium alloys contain about 60% cobalt and 25 to 30% chromium, with smaller amounts of other elements.

• A. Ti 5Al 4V
• B. Ti 6Al 4V
• C. Ti 5Al 5V
• D. Ti 6Al 6V

Explanation: Ti-6Al-4V is the most widely used titanium alloy in dental and medical applications because aluminium strengthens the alloy and vanadium…

• A. 19%
• B. 2%
• C. 1.7%
• D. 4%

Explanation: Steel used in dentistry is an iron-carbon alloy with carbon below about 2%, and the commonly quoted maximum is approximately 1.7%.

• A. Remove the oxides formed on the gold alloy
• B. Lower the melting point
• C. Replace casting wax
• D. Speed the burnout process

Explanation: Fluxes react with and dissolve surface oxides formed during heating, allowing molten alloy to flow and join properly.

• A. High quality iron
• B. Chrome
• C. Cobalt
• D. Nickel

Explanation: Chromium gives cobalt-chromium alloys corrosion resistance by forming a thin, adherent chromium oxide passive film on the surface.

• A. 3/8 inch
• B. ½ inch
• C. ¼ inch
• D. one inch

Explanation: A clearance of about 1/4 inch between the wax pattern and the ring end allows investment to surround the pattern adequately while…

• A. Decrease its strength and ability to be hardened
• B. Decrease its tarnish resistance
• C. Redden the alloy
• D. Increase its fusion temperature

Explanation: Platinum has a very high melting point, so adding a large amount raises the fusion temperature of a casting gold alloy.

• A. Gold added with palladium
• B. Gold added with calcium
• C. Gold with much of chromium
• D. Gold with silver

Explanation: White gold is produced by alloying gold with a white metal, classically palladium, platinum, nickel, or silver.

• A. 24 K
• B. 22 K
• C. 18 K
• D. 10 K

Explanation: Type II dental gold alloys are medium-strength alloys commonly made with about 18-karat gold.

• A. Composite
• B. Silver
• C. Gold
• D. Amalgam

Explanation: Gold is used in dentistry in an almost pure form, especially as direct filling gold or gold foil.

• A. Adaptation
• B. Annealing
• C. Wedging
• D. Atomic attraction and welding

Explanation: Gold foil is cohesive because clean gold surfaces attract atomically and cold-weld when brought into contact under pressure.

• A. 10 um
• B. 15 um
• C. 30 um
• D. 0.1 um

Explanation: The average particle size of powdered gold used for direct filling is about 15 micrometres.

• A. Cohesive gold
• B. Non cohesive gold
• C. Class I casting gold
• D. Class IV casting gold

Explanation: Cohesive gold is essentially pure gold whose surface is clean and able to weld to another gold surface during condensation.

• A. Gold and Platinum
• B. Gold and Calcium
• C. Cobalt and Chromium
• D. Tin and chromium

Explanation: Electralloy is a gold-calcium alloy associated with direct filling gold products. The other listed combinations do not identify this alloy.